This invention relates to display systems and, more particularly, to a combined laser recorder and projection system in which two channels of data are recorded by laser action on smectic liquid crystal display cells and are simultaneously projected, by back lighting the display cells, upon a display screen.
U.S. Pat. No. 3,961,334, which issued to Clyde M. Whitby and Douglas L. White on June 1, 1976, discloses a high speed, permanent recording, multicolor projection display system in which the beam of a pulsed laser is selectively deflected and focused to burn the desired images in a metalized film record medium which is back-illuminated for projecting the recorded images as they are produced. A channel selector polarizes the laser beam in either of two planes. The polarized channels are then selectively deflected and focused through a dichroic polarizer cube that transmits one channel and reflects the other channel to the metalized films in the focal planes where images are formed by thermal action. Simultaneously with the recording action, the images are projected by the use of white light that is split into two colored light beams by a second dichroic cube and is reflected to back light the images in each of the metalized films. The projected beams then pass back through the first dichroic cube where they either pass directly, as colored images, to the projection lens system, or are combined into white images before entering the projection lens system. Colored filters may be inserted into either or both of the projection lamp beams to produce various colored images. The disclosed system operates satisfactorily. However, the use of a metalized film as the recording medium possesses the disadvantage that a permanent image is formed. In order to change the image, other than by adding to it, the metalized film must be physically moved to a "clean" area and the image must be completely reformed. There are many applications where it would be desirable to be able to selectively change only certain areas of the image without affecting the remaining areas of the image.
It is therefore a primary object of this invention to provide a display system which may be selectively altered.